Bottom Line:
In the last few decades, supramolecular chemistry has been at the forefront of chemical research, with the aim of understanding chemistry beyond the covalent bond.Since the long-range periodicity in crystals is a product of the directionally specific short-range intermolecular interactions that are responsible for molecular assembly, analysis of crystalline solids provides a primary means to investigate intermolecular interactions and recognition phenomena.The discussion touches upon many of the prerequisites for controlled preparation and characterization of crystalline materials.

ABSTRACTIn the last few decades, supramolecular chemistry has been at the forefront of chemical research, with the aim of understanding chemistry beyond the covalent bond. Since the long-range periodicity in crystals is a product of the directionally specific short-range intermolecular interactions that are responsible for molecular assembly, analysis of crystalline solids provides a primary means to investigate intermolecular interactions and recognition phenomena. This article discusses some areas of contemporary research involving supramolecular interactions in the solid state. The topics covered are: (1) an overview and historical review of halogen bonding; (2) exploring non-ambient conditions to investigate intermolecular interactions in crystals; (3) the role of intermolecular interactions in morphotropy, being the link between isostructurality and polymorphism; (4) strategic realisation of kinetic coordination polymers by exploiting multi-interactive linker molecules. The discussion touches upon many of the prerequisites for controlled preparation and characterization of crystalline materials.

fig5: One-dimensional chains formed by Br2 (working as a bidentate XB donor) with 1,4-dioxane (a) and benzene (b), both working as bidentate XB acceptors. H atoms are omitted. XBs are shown as black dotted lines. Distances are given in Å and angles in degrees. Colour code: grey, C; red, O; brown, Br.

Mentions:
Description of various observations and phenomena where we now recognize the role played by XB went on through the entire 20th century. Most of the important discoveries reported in the last 70 years are summarized below. In 1948, UV–vis spectroscopy allowed the I2–benzene complex to be identified in solution and 1 year later other aromatics were reported to behave analogously (Benesi & Hildebrand, 1949 ▸). R. S. Mulliken described in 1950 the formation of similar complexes with ethers, thioethers and carbonyl derivatives (Mulliken, 1950 ▸) and 2 years later he rationalized them as a subclass of the electron donor–acceptor molecular complexes (Mulliken, 1952 ▸). The appearance in UV–vis spectra of bands specific for charge transfer from the electron-density donor to the halogen atom was shown by complexes involving dihalogens and aromatics (Rosokha & Kochi, 2008 ▸) and by many other halogen-bonded adducts, even as weak as the perfluoro­carbon/amine complexes (Burdeniuc et al., 1998 ▸). The Br2⋯O(CH2CH2)2O adduct was the first reported X-ray structure of a halogen-bonded system (Hassel et al., 1954 ▸; Fig. 5 ▸a) and several related crystal structures of adducts involving dihalogens and halocarbons were then established in rapid sequence (Hassel, 1970 ▸). The crystal structures of Br2⋯C6H6 (Fig. 5 ▸b) and Cl2⋯C6H6 (Hassel et al., 1959 ▸) are particularly noteworthy as they proved that π-systems work as donors of electron density to electrophilic halogens also in the solid state (Vasilyev et al., 2001 ▸). Importantly, these systems suggested that halogen-bonded adducts are on the reaction pathways of halogenation reactions of aromatics and other unsaturated systems. In the successive decades, this hypothesis was forcefully confirmed (Lenoir & Chiappe, 2003 ▸) and it was shown that π-donating units form solid adducts also with halocarbons (Rosokha & Kochi, 2008 ▸).

fig5: One-dimensional chains formed by Br2 (working as a bidentate XB donor) with 1,4-dioxane (a) and benzene (b), both working as bidentate XB acceptors. H atoms are omitted. XBs are shown as black dotted lines. Distances are given in Å and angles in degrees. Colour code: grey, C; red, O; brown, Br.

Mentions:
Description of various observations and phenomena where we now recognize the role played by XB went on through the entire 20th century. Most of the important discoveries reported in the last 70 years are summarized below. In 1948, UV–vis spectroscopy allowed the I2–benzene complex to be identified in solution and 1 year later other aromatics were reported to behave analogously (Benesi & Hildebrand, 1949 ▸). R. S. Mulliken described in 1950 the formation of similar complexes with ethers, thioethers and carbonyl derivatives (Mulliken, 1950 ▸) and 2 years later he rationalized them as a subclass of the electron donor–acceptor molecular complexes (Mulliken, 1952 ▸). The appearance in UV–vis spectra of bands specific for charge transfer from the electron-density donor to the halogen atom was shown by complexes involving dihalogens and aromatics (Rosokha & Kochi, 2008 ▸) and by many other halogen-bonded adducts, even as weak as the perfluoro­carbon/amine complexes (Burdeniuc et al., 1998 ▸). The Br2⋯O(CH2CH2)2O adduct was the first reported X-ray structure of a halogen-bonded system (Hassel et al., 1954 ▸; Fig. 5 ▸a) and several related crystal structures of adducts involving dihalogens and halocarbons were then established in rapid sequence (Hassel, 1970 ▸). The crystal structures of Br2⋯C6H6 (Fig. 5 ▸b) and Cl2⋯C6H6 (Hassel et al., 1959 ▸) are particularly noteworthy as they proved that π-systems work as donors of electron density to electrophilic halogens also in the solid state (Vasilyev et al., 2001 ▸). Importantly, these systems suggested that halogen-bonded adducts are on the reaction pathways of halogenation reactions of aromatics and other unsaturated systems. In the successive decades, this hypothesis was forcefully confirmed (Lenoir & Chiappe, 2003 ▸) and it was shown that π-donating units form solid adducts also with halocarbons (Rosokha & Kochi, 2008 ▸).

Bottom Line:
In the last few decades, supramolecular chemistry has been at the forefront of chemical research, with the aim of understanding chemistry beyond the covalent bond.Since the long-range periodicity in crystals is a product of the directionally specific short-range intermolecular interactions that are responsible for molecular assembly, analysis of crystalline solids provides a primary means to investigate intermolecular interactions and recognition phenomena.The discussion touches upon many of the prerequisites for controlled preparation and characterization of crystalline materials.

ABSTRACTIn the last few decades, supramolecular chemistry has been at the forefront of chemical research, with the aim of understanding chemistry beyond the covalent bond. Since the long-range periodicity in crystals is a product of the directionally specific short-range intermolecular interactions that are responsible for molecular assembly, analysis of crystalline solids provides a primary means to investigate intermolecular interactions and recognition phenomena. This article discusses some areas of contemporary research involving supramolecular interactions in the solid state. The topics covered are: (1) an overview and historical review of halogen bonding; (2) exploring non-ambient conditions to investigate intermolecular interactions in crystals; (3) the role of intermolecular interactions in morphotropy, being the link between isostructurality and polymorphism; (4) strategic realisation of kinetic coordination polymers by exploiting multi-interactive linker molecules. The discussion touches upon many of the prerequisites for controlled preparation and characterization of crystalline materials.